Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

A backdoor to Machu Picchu that only the most foolhardy infiltrator would attempt to breach.

The bones of this aquatic dinosaur turned to opal over the centuries and the beast's remains were almost sold as jewelry.

This historic observatory contains the world's oldest refracting lens telescope.

The first life claimed by this record-breaking peak wasn't lost to exposure or a fall, but rather lightning.

Once a bustling cotton factory, this early 20th-century building is now home to a thriving artspace.

Art deco landmark on the outskirts of Washington, D.C.

Obscure Freemasons still live in D.C.’s largest private residence.

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

The site of the climactic scene from the classic horror film is now a historic landmark.

A building shaped like the Army Corps of Engineers logo, because why not?

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

The only place for a truly presidential dram.

This twice-relocated "Usonian" home is among the smallest built by master architect Frank Lloyd Wright.

Thomas Jefferson's estate is home to hundreds of varieties of historic fruits and vegetables.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Near-constant high winds deform the trees on Spruce Knob, the highest point in West Virginia.

Pennsylvania's highest point is spotted with boulders which were pushed to the surface by nothing but cold.

This claimant to the title of "smallest church in the 48 states" doubles as an equally tiny, quasi-post office.

The highest point in Maryland is only accessible by hiking through another state.

Inside this store, a mysterious statue draws visitors from the world over.

A UFO scrapyard in the California desert.